The UK's most complete GLP-1 guide
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- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Is 5mg Mounjaro Equivalent to Wegovy?
If you're researching weight loss injections, you've likely seen "5mg Mounjaro equivalent to Wegovy" mentioned. The short answer: approximate equivalence exists, but these are different medications with different mechanisms. Both are prescription-only in the UK and require clinical assessment. Individual suitability depends on your health profile, not which one is "stronger". Let's break down how they compare and what the equivalence actually means.
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What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Mounjaro and Wegovy Work Differently
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. This means it activates two separate hormone pathways — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). The dual mechanism may explain why clinical trials showed slightly higher average weight loss with Mounjaro compared to Wegovy.
Wegovy (semaglutide) is a GLP-1-only receptor agonist. It activates the single GLP-1 pathway. In the STEP clinical trials, Wegovy at its maximum dose of 2.4 mg achieved average weight loss of approximately 14.9% of body weight over 68 weeks, when used alongside a reduced-calorie diet and increased physical activity.
The approximate dose equivalence (5mg Mounjaro ≈ 0.5 mg Wegovy, 10mg Mounjaro ≈ 1.7 mg Wegovy, 15mg Mounjaro ≈ 2.4 mg Wegovy) is based on clinical practice guidance, not an official conversion chart. Any switch between medications must be managed by your prescriber.
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Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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Individual Suitability Matters More Than Equivalence
Because Mounjaro and Wegovy use different mechanisms, they may not be truly "equivalent" for every person. Some patients respond better to dual GIP/GLP-1 action, while others do equally well on GLP-1 alone. Factors your prescriber will consider include your current health conditions, other medications you're taking, any previous experience with GLP-1 injections, and how your body tolerates medication.
Both medications are available via NHS specialist weight management services (though with significant regional variation and waiting times) or through private online prescribing following clinical assessment. Neither is available over-the-counter. Your GP or licensed prescriber will assess which option, if either, is appropriate for you. Use our GLP-1 weight loss calculator to explore projected outcomes, and try our BMI calculator to understand your personal baseline.
Trial data comparison: In SURMOUNT-1 trials, 15mg Mounjaro achieved average weight loss of approximately 20.9% of body weight at 72 weeks. Wegovy at 2.4 mg achieved 14.9% in STEP-1 trials. These averages include patients using medication alongside lifestyle changes — individual results vary significantly. Neither medication assures weight loss.
Prescribers typically choose based on: your response to GLP-1 previously (if any), whether you have type 2 diabetes or prediabetes (both help with blood sugar), side effect profile tolerability, and what's available through your access route (NHS or private). Switching between them is possible but requires clinical oversight and may involve a washout period.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
What does "5mg Mounjaro equivalent to Wegovy" actually mean?
It's an approximate dose equivalence used in clinical practice. 5mg Mounjaro is thought to produce similar weight loss outcomes to approximately 0.5mg Wegovy. However, these are different medications with different mechanisms — direct equivalence isn't assured for every individual. Any switch must be supervised by your prescriber, and there's no official MHRA-approved conversion chart.
Is Mounjaro stronger than Wegovy?
"Stronger" isn't the right way to think about it. Mounjaro uses a dual mechanism (GIP+GLP-1), while Wegovy uses GLP-1 alone. Clinical trials showed Mounjaro achieved slightly higher average weight loss, but individual results vary. Neither is universally "better" — suitability depends on your personal health profile and how you respond to the medication.
Can I switch from Wegovy to Mounjaro?
Yes, switching is possible in the UK, but only under prescriber guidance. You cannot self-switch between prescription medications. Your GP or specialist will advise whether switching is appropriate, and may suggest a specific transition protocol. Both require ongoing clinical assessment.
How do I know which one is right for me?
You don't choose — your prescriber does, based on your health history, current medications, previous GLP-1 response (if any), and clinical assessment. Both are prescription-only and require a formal clinical consultation. Your suitability is individual, not based on trial averages.
What if I've heard about Mounjaro through a UK pharmacy or other pharmacies?
Mounjaro is available through NHS specialist services or private online prescribing with a UK-licensed prescriber. Availability and cost vary by route. Any pharmacy dispensing Mounjaro in the UK must be GPhC-registered. Always check the prescriber's credentials before ordering online.
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